To enhance the aesthetical appearance of low cost fibrous webs, such as non-woven polishing or washing cloths, it is common practice in the industry to imprint on the fibrous web a decorative pattern. Typically, this operation is carried out immediately after the web has been formed, at a printing station operating according to the principle of a common printing press. The printing station comprises a printing roll which is engraved to form a shaped colorant transfer zone applying colorant, such as ink, according to a desired pattern on the surface of the fibrous web maintained in rolling contact with the printing roll.
When the colorant transfer surface is of a relatively small extent, having a maximum axial dimension (herein "axial dimension" shall mean the dimension measured along an imaginary line parallel to the rotation axis of the printing roll) less than the length of the printing roll, it has been observed that the printing station has a tendency to become clogged by dirt particles normally present in the environment of the printing station, such as small fibers released from the fibrous web or airborne impurities, which accumulate under the doctor blade provided to scrape excess colorant from the printing roll. When the build-up of particles increases beyond a certain point where the doctor blade is no longer capable of maintaining firm contact with the relief surface of the printing roll, excess colorant is carried over the fibrous web which produces undesirable spots or streaks.
A possible solution to this problem is to clean the doctor blade at short intervals to remove the build-up of impurities, however, this would require frequent interruptions of the entire production line.